The present invention relates to a short takeoff jump mode for airplane telescoping energy-dissipating oleo landing gear struts. More particularly, the invention relates to a method and a jump strut device resulting in early takeoff of an airplane or, alternatively, more airplane payload without ground roll increase.
In years past, various devices relating to vertically accelerating an airplane during its takeoff roll have been patented. Examples of these are shown by U.S. Pat. Nos. 1,254,898, 1,317,414 and 1,702,682 which suggest projecting separate takeoff struts downwardly to impact the ground and by extension raise the airplane into the air with rotation or extension of the struts, U.S. Pat. Nos. 1,068,165 and 1,767,120, which show the extension of the landing gear wheels, and U.S. Pat. No. 1,745,081, which pivots an undercarriage through an arc in order to raise the airplane from the ground, which is a major departure from standard design practice. These prior art teachings do not suggest very practical direct integration and use of the concept of jumping an airplane with the use of a telescoping, energy-dissipating oleo shock absorber. These prior art teachings rely on the landing gear which act like springs and temporarily store energy, but do not directly dissipate it.
In fact, efforts to provide short takeoff capability on recent airplane designs have focused on more thrust and/or tilted thrust from the propulsion system, and wings that lift more at low speeds, rather than improved landing gears. An exception to this is the use by the British Royal Navy of an inclined ramp on an aircraft carrier forward deck to launch the airplane in a trajectory which is initially upward.
An obvious problem with this ramp technique for an airplane operating on land is that the ramp must always be at the upwind end of the runway, and the downwind end of the runway must be unobstructed. Since shifting wind direction is a nearly omnipresent condition, the ramp must frequently be relocated.
Another obvious problem with this ramp concept is the loading of the airplane undercarriage mounting in an unfamiliar pattern, which can result in a requirement for extensive structural modifications with consequent cost and performance penalties.
A frequent problem during the takeoff run of a nose wheel airplane with a high ratio of engine thrust to airplane weight and a low wing is that the sum of the nose down thrust couple and airplane weight moment about the main wheel axis exceeds the available nose up aerodynamic control moment until a high speed is reached. Thus, the airplane cannot lift off the ground, even though it may have enough speed to generate adequate lift if the proper high angle of attack could be achieved.
The principal object of the present invention is to provide a short ground run or overload jump takeoff method and device for telescopic, energy-dissipating oleo airplane landing gear shock struts neither of which method nor device requires significant change in the landing gear installation, or the airplane structure, aerodynamics, or propulsion design, which does not involve departures from the standard stability and control flight envelope of the airplane, and which requires no elaborate ground-based equipment.
An object of the invention is to provide a method and device for increasing the angle of attack of the airplane at an early point in its takeoff roll to increase the lift and permit a shorter takeoff ground run or payload increase, which method requires no significant change in the landing gear installation, or the airplane configuration, structure, aerodynamics, or propulsion design, and which requires no elaborate ground-based equipment.
Another object of the invention is to couple to the telescoping, energy-dissipating oleo landing gear shock absorber of a state-of-the-art airplane a system for varying its gas pressure loading, to effect initial latching thereof, and thereafter to pressurize same to force rapid extension thereof upon release of the latch, with quick reversion to the shock dissipation mode, thereby to provide early takeoff or payload increase of the airplane.
Still another object of the invention is to provide a jump strut device of simple structure which reverts quickly to the shock dissipation mode and which provides a short takeoff or payload increase for an airplane via the telescoping, energy-dissipating oleo landing gear shock struts of the airplane.
Yet another object of the invention is to provide a jump strut device which is inexpensive in manufacture and maintained with facility and convenience, providing early takeoff or payload increase of an airplane.
Another object of the invention is to provide a jump strut device for short takeoff or increased payload of an airplane with efficiency, effectiveness, reliability and safety.